He told The New York Times: "I was kind of in a mental fog, and it had nothing to do with the booze.

"My mind wasn't right. I wasn't focused. I went into a deep, deep depression after 9/11.

"9/11 just knocked the wind out of me, and I don't know even now if I've recovered from it. It really, really hurt that man could do that to man."

Joel admitted that he doesn't "subscribe" to the 12-step programme by Alcoholics Anonymous and has "a glass of wine once in a while".

Joel also responded to previous touring partner Elton John, who suggested that he had stopped songwriting "out of fear or laziness" and needed to take rehab more seriously.

He replied: "He doesn't know anything about my private life. He's a very friendly, charming man, a nice fun guy, but we really never spent much time personally together... I'd work with him again, sure."